Buggy code:
public class MailOptionsDialog extends JDialog implements ActionListener { protected JButton okButton ; protected JButton cancelButton ; protected JButton helpButton ; protected CheckBoxWithMnemonic markCheckBox ; protected JSpinner markSpinner ; protected CheckBoxWithMnemonic preferHtmlCheckBox ; protected CheckBoxWithMnemonic disableHtmlCheckBox ; protected CheckBoxWithMnemonic enableSmiliesCheckBox ; protected CheckBoxWithMnemonic quotedColorCheckBox ; protected JButton quotedColorButton ; protected JCheckBox emptyTrashCheckBox ; protected CheckBoxWithMnemonic emptySubjectCheckBox ; protected CheckBoxWithMnemonic sendHtmlMultipartCheckBox ; protected CheckBoxWithMnemonic showAttachmentsInlineCheckBox ; private JLabel selectedBrowserLabel ; protected JComboBox selectedBrowserComboBox ; protected LabelWithMnemonic forwardLabel ; protected JComboBox forwardComboBox ; public MailOptionsDialog ( JFrame frame ) { } public void updateComponents ( boolean b ) { } protected void initComponents ( ) { markCheckBox = new CheckBoxWithMnemonic ( MailResourceLoader . getString ( "dialog" , "general" , "mark_messages_read" ) ) ; markSpinner = new JSpinner ( ) ; markSpinner . setModel ( new SpinnerNumberModel ( 1 , 0 , 99 , 1 ) ) ; emptyTrashCheckBox = new CheckBoxWithMnemonic ( MailResourceLoader . getString ( "dialog" , "general" , "empty_trash" ) ) ; emptyTrashCheckBox . setEnabled ( false ) ; enableSmiliesCheckBox = new CheckBoxWithMnemonic ( MailResourceLoader . getString ( "dialog" , "general" , "enable_smilies" ) ) ; quotedColorCheckBox = new CheckBoxWithMnemonic ( MailResourceLoader . getString ( "dialog" , "general" , "color_quoted_text" ) ) ; quotedColorButton = new JButton ( "..." ) ; quotedColorButton . setActionCommand ( "COLOR" ) ; quotedColorButton . addActionListener ( this ) ; preferHtmlCheckBox = new CheckBoxWithMnemonic ( MailResourceLoader . getString ( "dialog" , "general" , "prefer_html" ) ) ; disableHtmlCheckBox = new CheckBoxWithMnemonic ( MailResourceLoader . getString ( "dialog" , "general" , "disable_html" ) ) ; emptySubjectCheckBox = new CheckBoxWithMnemonic ( MailResourceLoader . getString ( "dialog" , "general" , "ask_on_empty_subject" ) ) ; sendHtmlMultipartCheckBox = new CheckBoxWithMnemonic ( MailResourceLoader . getString ( "dialog" , "general" , "send_html_multipart" ) ) ; forwardLabel = new LabelWithMnemonic ( MailResourceLoader . getString ( "dialog" , "general" , "forward_as" ) ) ; String [ ] items = new String [ ] { MailResourceLoader . getString ( "dialog" , "general" , "forward_as_attachment" ) , MailResourceLoader . getString ( "dialog" , "general" , "forward_as_quoted" ) } ; forwardComboBox = new JComboBox ( items ) ; showAttachmentsInlineCheckBox = new CheckBoxWithMnemonic ( "Show<seq2seq4repair_space>Attachments<seq2seq4repair_space>&Inline" ) ; showAttachmentsInlineCheckBox . setActionCommand ( "ATTACHMENTS_INLINE" ) ; showAttachmentsInlineCheckBox . addActionListener ( this ) ; selectedBrowserLabel = new JLabel ( "Message<seq2seq4repair_space>Renderer" ) ; Vector < String > v = new Vector < String > ( ) ; try { <START_BUG> IExtensionHandler handler = PluginManager . getInstance ( ) . getHandler ( ORG_COLUMBA_CORE_HTMLVIEWER ) ; <END_BUG> Enumeration e = handler . getExtensionEnumeration ( ) ; while ( e . hasMoreElements ( ) ) { IExtension ext = ( ( IExtension ) ( e . nextElement ( ) ) ) ; String id = ext . getMetadata ( ) . getId ( ) ; v . add ( id ) ; } } catch ( PluginHandlerNotFoundException e ) { e . printStackTrace ( ) ; } selectedBrowserComboBox = new JComboBox ( v . toArray ( new String [ 0 ] ) ) ; selectedBrowserComboBox . setSelectedIndex ( 0 ) ; selectedBrowserComboBox . setActionCommand ( "USE_DEFAULT_BROWSER" ) ; selectedBrowserComboBox . addActionListener ( this ) ; okButton = new org . columba . core . gui . base . ButtonWithMnemonic ( MailResourceLoader . getString ( "global" , "ok" ) ) ; okButton . setActionCommand ( "OK" ) ; okButton . addActionListener ( this ) ; cancelButton = new org . columba . core . gui . base . ButtonWithMnemonic ( MailResourceLoader . getString ( "global" , "cancel" ) ) ; cancelButton . setActionCommand ( "CANCEL" ) ; cancelButton . addActionListener ( this ) ; helpButton = new org . columba . core . gui . base . ButtonWithMnemonic ( MailResourceLoader . getString ( "global" , "help" ) ) ; HelpManager . getInstance ( ) . enableHelpOnButton ( helpButton , "configuring_columba_7" ) ; HelpManager . getInstance ( ) . enableHelpKey ( getRootPane ( ) , "configuring_columba_7" ) ; } protected void layoutComponents ( ) { } public void actionPerformed ( ActionEvent event ) { } }

Fix:
IExtensionHandler handler = PluginManager . getInstance ( ) . getExtensionHandler ( ORG_COLUMBA_CORE_HTMLVIEWER ) ;